Cylindrical tool for thin sample grinding and polishing

ABSTRACT

The design of a stainless-steel cylindrical tool for manual grinding and polishing of cement-based thin sample (two cylinders one within the other, connected by the movable threaded holder with a plate, that passes through the middle) enables very precise removal of sample layers to its thickness of 1-mm ( 1/32 inch) and less. The squared, young aged sample rests on the circular plate on a holder, that can be slowly and safely rotated during thin layer removal, to obtain a smooth and flat sample surface, which can produce sharp digital images in ESEM, necessary for detailed and accurate image analysis. The cylindrical tool can be reassembled. It is reusable, easy to maintain and clean. Its design is practical since inner cylinder can be replaced if damaged, with the identically designed inner cylinder or with differently designed inner cylinder adjusted to another sample size.

1. BACKGROUND OF THE INVENTION

I. The challenge of proper preparation of cement-based samples appeared when micro-scale non-destructive experiments on drying shrinkage and microcracking in Environmental Scanning Electron Microscope (ESEM) needed to be performed on 1-mm thick samples at their young age (2-3 days old). The examination of such thin samples, was first suggested in the literature to enable the uniform sample drying. By examining such thin sample, it is possible to avoid the development of a moisture gradient, which would normally appear in the case of larger and thicker cement-based samples. The suggested 1-mm ( 1/32 inch) sample thickness was applicable in drying shrinkage and microcracking experiments in ESEM, due to the characteristic climate conditions (relative humidity) in ESEM chamber. However, at such young age (2-3 days old), thin samples made of cementitious materials crumble easily during handling.

II. For the preparation of such thin cement-based samples for testing in ESEM, it is very important that sample surface remains undamaged, smooth and freshly polished before the test, in order to obtain a digital image as sharp as possible for further image analysis using Digital Image Analysis. Since these ESEM digital images are generated at micro-scale, at the magnification below 5 μm, precision in sample preparation is crucial for accurate experimental results and precise detection of deformation and (possible) appearance of microcracks that may occur due to uneven sample shrinkage. It is therefore necessary, before beginning of ESEM experiments, to prepare (grind and polish) the sample surface to be completely smooth to avoid contrast reduction in digital image. Equally important is to avoid the appearance of (micro)cracks as the result of sample preparation and not as the result of drying experiments.

III. Grinding and polishing of larger and already harden samples by a tool or hand is typically done on a grinding machine, with two rotating wheels, where the special sandpaper of different granulation is attached at each wheel. However, no tool for grinding and polishing of larger samples could be used to prepare such thin and sensitive sample. Some researchers who worked on similar tests in ESEM, would manually polish smaller sample-flakes (age 7 days and above) directly by hand, after obtaining them by breaking larger (typically) prismatic sample with a hammer (Neubauer et al.). Such sample preparation would produce an uneven sample and it would ruin the sample microstructure before the test.

IV. The inventor* of the current cylindrical tool previously invented a mould for casting samples of 2-mm ( 1/16 inch) thickness. Therefore, it was necessary to invent a way in which such 2-mm ( 1/16 inch) thick samples could be grind and polished without breaking or damaging them while obtaining the smooth and fresh sample surface. Neither any tools for grinding and polishing of such thin, young cement-based sample nor an established method for the preparation of 1-mm ( 1/32 inch) thick samples, was known to the current inventor* at the time of cylindrical tool invention. *Inventor: MSc Dragana Janković, Structural Civil Engineer, UCF, FL

REFERENCE

Neubauer, C. M., Jennings H. M. and Garboczi E. J. Mapping drying shrinkage deformations in cement-based materials, Cement and Concrete Research, Vol. 27, no. 10 (1997), pp. 1603-1612.

2. BRIEF SUMMARY OF INVENTION

In order to manually prepare thin sample of cementitions materials for the observation of drying shrinkage and microcracking in the electron microscope (ESEM), a cylindrical stainless-steel tool is constructed. The three-part tool consists of outer and smaller inner cylinder and handle with a plate. The tool enables grinding and polishing of a thin sample, 2 mm ( 1/16 inch) thick, to the desired thickness of 1-mm ( 1/32 inch) and below thanks to: (a) rotational circular plate with a threaded handle, placed through the center of both cylinders, on which sample is placed, (b) safe sample holding in the specially designed opening in the inner cylinder, (c) circular scale, engraved at the top of outer cylinder, at the opposite end of the sample location, (d) notch and marker on the plate handle, that are used to rotate plate with a screwdriver and to mark the numbers on the circular scale, respectively, to check the sample thickness in the process of grinding and polishing. Based on such sample surface preparation prior to testing, the obtained digital images during drying tests in ESEM are extremely sharp. The cylindrical tool is constructed to be disassembled and reassembled except for the plate and handle, which are made as a whole. The cylindrical tool is multipurpose, easy to handle and maintain, with the possibility of replacement of the inner cylinder and plate with a handle. Namely, two inner cylinders for grinding and polishing of a sample of different size, are designed to fit in one outer larger cylinder, one at the time. The two inner cylinders differ in the size of inner opening and two plates differ in the size of the diameter. They are adjusted for samples with different dimensions: 10×10×2 mm (⅜×⅜× 1/16 inch) or 30×30×2 mm ( 9/8× 9/8× 1/16 inch).

3. BRIEF DESCRIPTION OF DRAWINGS Disassembled Stainless Steel Cylindrical Tool for Small Sample Preparation

FIG. 1 . Side view of the empty outer stainless steel cylinder, with visible not-fully-polished, ‘ring’-like lower part and indicated (marked) inner opening for holder and inner (smaller) cylinder, as well as vertical cross section (1-1) and upper view (2-2) of outer cylinder.

FIG. 1A. Vertical cross section (1-1) through empty outer cylinder, with visible threaded opening for the holder and lined thin A1 sheets around the opening for the inner cylinder placement.

FIG. 1B. Upper view (2-2) of the empty outer cylinder with the visible opening for the holder around which the scale (0-4) is engraved and marked opening for inner cylinder.

FIG. 2 . Side view of the empty stainless steel inner cylinder with marked opening for the holder and small plate for 10×10×2 mm (⅜×⅜× 1/16 inch) sample holding as well as cylinder vertical cross section (3-3), upper view (4-4) and bottom view (5-5).

FIG. 2A. Vertical cross section (3-3) through empty inner cylinder so that threaded opening for the holder and inner opening with surrounding “wall” (edge), for the plate and sample (10×10×2 mm or ⅜×⅜× 1/16 inch), is visible.

FIG. 2B. Upper view (4-4) of the inner cylinder with the visible circular holder opening.

FIG. 2C. Bottom view (5-5) of the inner cylinder with visible circular hole for the holder from the bottom part and opening with surrounding “walls” (edges), where the plate and sample (10×10×2 mm or ⅜×⅜× 1/16 inch) are placed.

FIG. 3 . Side view of the stainless steel threaded holder with a plate for 10×10×2 mm (⅜×⅜× 1/16 inch) sample holding.

FIG. 3A. Upper view (6-6) of the circular holder end, where the notch and marker are engraved.

FIG. 3B. Bottom view (7-7) of the circular plate at the holder end for 10×10×2 mm (⅜×⅜× 1/16 inch) sample holding.

Disassembled Stainless Steel Cylindrical Tool for Large Sample Preparation

New Figure Numbering from Replacement Sheet

FIG. 10 . Side view of the empty outer stainless steel cylinder, with visible not-fully-polished, ‘ring’-like lower part and indicated (marked) inner opening for holder and inner (smaller) cylinder, as well as vertical cross section (18-18) and upper view (19-19) of outer cylinder.

FIG. 10A. Vertical cross section (18-18) through empty outer cylinder, with visible threaded opening for the holder and lined thin A1 sheets around the opening for the inner cylinder placement.

FIG. 10B. Upper view (19-19) of the empty outer cylinder with the visible opening for the holder around which the scale (0-4) is engraved and marked opening for inner cylinder.

FIG. 4 . Side view of the empty inner cylinder with marked opening for the holder and larger plate for 30×30×2 mm ( 9/8× 9/8× 1/16 inch) sample holding as well as vertical cross section (8-8), upper view (9-9) and bottom view (10-10).

FIG. 4A. Vertical cross section (8-8) through empty inner cylinder so that threaded opening for the holder and inner opening for plate and 30×30×2 mm ( 9/8× 9/8× 1/16 inch) sample holding is visible.

FIG. 4B. Upper view (9-9) of the inner cylinder with the visible circular holder opening.

FIG. 4C. Bottom view (10-10) of the inner cylinder with visible circular hole for the holder and opening with surrounding half-circled “walls” (edges) for placing plate and sample (30×30×2 mm or 9/8× 9/8× 1/16 inch).

FIG. 5 . Side view of the threaded holder with a plate for 30×30×2 mm ( 9/8× 9/8× 1/16 inch) sample holding.

FIG. 5A. Upper view (11-11) of the circular holder end, where the notch and marker are engraved.

FIG. 5B. Bottom view (12-12) of the circular plate at the holder end for 30×30×2 mm ( 9/8× 9/8× 1/16 inch) sample holding.

Assembled Stainless Steel Cylindrical Tool

FIG. 6 . Side view of assembled stainless steel cylindrical tool with marked threaded holder with a plate and inner cylinder for 10×10×2 mm (⅜×⅜× 1/16 inch) sample and visible not-fully-polished ‘ring’ around the lower part of outer cylinder; the upper and bottom view of assembled cylinder are marked.

FIG. 6A. Upper view of assembled cylindrical tool (13-13) with: visible engraved circular scale with numbers (0-4), holder end with engraved notch and marker, and marked inner cylinder and circular plate for 10×10×2 mm (⅜×⅜× 1/16 inch) sample holding.

FIG. 6B. Bottom view of assembled cylindrical tool (14-14), where inner cylinder with its bottom opening and circular plate for 10×10×2 mm (⅜×⅜× 1/16 inch) sample holding are visible, while circular holder end is marked.

FIG. 7 . Side view of assembled stainless steel cylindrical tool with marked threaded holder with a plate and inner cylinder for 30×30×2 mm ( 9/8× 9/8× 1/16 inch) sample and visible not-fully-polished ‘ring’ around the lower part of outer cylinder.

FIG. 7A. Upper view of the assembled cylindrical tool (15-15) with visible engraved circular scale with numbers (0-4), holder end with engraved notch and marker, and marked inner cylinder and circular plate for 30×30×2 mm ( 9/8× 9/8× 1/16 inch) sample holding.

FIG. 7B. Bottom view of the assembled cylindrical tool (16-16), where inner cylinder with its bottom opening and circular plate for 30×30×2 mm ( 9/8× 9/8× 1/16 inch) sample holding are visible, while circular holder end is marked.

4. DETAILED DESCRIPTION OF INVENTION

I. The stainless steel cylindrical tool is designed to hold an early aged (2-3 days old and above) thin sample 2 mm ( 1/16 inch) thick during manual grinding and polishing to 1-mm ( 1/32 inch) thickness or less, without damaging or breaking it. The invention of cylindrical tool followed the invention of the stainless-steel mould for thin sample casting from the same inventor*.

II. The stainless steel cylindrical tool consists of three parts: outer (larger) cylinder, FIGS. 1, 1A, 1B and FIGS. 10, 10A, 10B, inner (smaller) cylinder, FIGS. 2, 2A-2C, and holder with a plate, FIGS. 3, 3A, 3B (for the sample size 10×10×2 mm or ⅜×⅜× 1/16 inch). Both cylinders can be disassembled and reassembled again except for the holder and plate as they form a whole. The disassembling and reassembling enable a thorough cleaning of the cylindrical tool after sample preparation. It also gives the possibility of the insertion of another inner cylinder (FIGS. 4, 4A-4C) with the holder and plate (FIGS. 5, 5A, 5B) for the larger sample 30×30×2 mm ( 9/8× 9/8× 1/16 inch) preparation.

III. The total height of the cylindrical tool is determined by the total height of the outer cylinder, which is 45 mm (9 3/16 inch). The outer cylinder has an additional ‘ring’-like outer layer (FIGS. 1, 10, 6, 7 ) as a result of mechanical steel processing, where this part of outer cylinder is left as not-fully-polished. As a consequence, the diameter of outer cylinder is reduced from ϕ60 (9 2/8 inch) at the bottom and up to 11 mm (⅜ inch) height, to ϕ58 (3 6/8 inch) at the remaining height of 34 mm (1⅛ inch). The ‘ring’-like layer enables easier handling of the heavy tool during grinding and polishing.

IV. The inner cylinder is 22.5 mm (9 3/32 inch) high, with diameter ϕ39.5 ( 3/2 inch). Two inner cylinders, FIGS. 2, 2A-2C vs. FIGS. 4, 4A-4C, differ in the design and the size of the inner opening, which is created as a free space for the vertical movement of circular plate (FIGS. 2C, 4C).

V. The smooth fitting of any of two inner cylinders to the outer cylinder is done by making a circular opening ϕ40.5 ( 3/2 inch) and 22.5 mm (9 3/32 inch) high in the outer cylinder (FIGS. 1A and 10A) for the placement of inner cylinder(s), FIGS. 2, 4, 6, 7 . Easier pulling out of the inner cylinder and the prevention of any friction between outer and inner cylinder during the tool disassembling or reassembling, is done by vertically inserting nine thin A1 sheets 5 mm ( 3/16 inch) wide, 22.5 mm (9 3/32 inch) high at the circular distance of 8 mm ( 5/16 inch) in the circular opening, fixed to the rounded 3 mm (⅛ inch) high slot, FIG. 1A, 10A.

VI. The rounded holder ϕ8 ( 5/16 inch) is 45 mm (9 3/16 inch) long, merged with the rounded plate ϕ10 (⅜ inch) or ϕ30 ( 9/8 inch), which is 3 mm (⅛ inch) thick, FIGS. 3, 5 . The plate holder has horizontal threads at each 0.25 mm ( 3/320 inch), from top of the holder till 2 mm ( 1/16 inch) above the plate due to mechanical processing. The same threads are also engraved in the outer cylinder opening (height 17.5 mm or ⅝ inch) and inner cylinder opening (height 14.5 mm or ½ inch), FIGS. 1A, 10A, 2A, 4A, in order to assemble both cylinders with the holder. The holder and plate can rotate with a help of a notch that is 1 mm ( 1/32 inch) wide and 8 mm long ( 5/16 inch), FIGS. 3A, 5A, 6A, 7A, and a screwdriver.

VII. The circular plate, FIGS. 3B, 5B, 6, 7 serves as a sample carrier. In order to easily move holder and the plate up and down, through the vertical threaded hole in the cylinders, the plate must be rounded, not squared, although the cement-based samples are squared. The cylindrical shape of the tool is also more practical for handling, in comparison to any other shape. In order to control a thickness of a sample-layer during its removal, the rounded scale with numbers (0-4) is engraved at the top of the outer cylinder (FIG. 1B, 10B, 6A, 7A), where the holder of the rounded plate sticks out for 3 mm (⅛ inch), FIGS. 6, 7 .

VIII. A smaller marker 4 mm (⅛ inch) long engraved vertically to the notch, is used to mark one of the numbers on the scale (0-4), FIGS. 3A, 5A, 6A, 7A during plate rotation. The depth of the bottom opening in inner cylinder(s) is 8 mm ( 5/16 inch), FIGS. 2A, 4A, while the size of plate (ϕ10 or ⅜ inch), FIG. 3B or ϕ30 ( 9/8 inch), FIG. 5B, ‘dictates’ the width of the openings in both inner cylinders, FIGS. 2C, 4C, 6B, 7B.

IX. The five short horizontal marks are engraved on the inner “walls” (edges) around the openings in the inner cylinders, FIGS. 2A, 4A. They are about 5 mm ( 3/16 inch) long. They are used to help measuring (doublecheck) the sample thickness during sample layer removal. The four small rounded openings (ϕ4 or 5/32 inch), on the bottom of the inner cylinder for 10×10×2 mm (⅜×⅜× 1/16 inch), FIGS. 2C, 6B are made for the safety of the sample corners, in order to prevent the sample corners from breaking, during grinding and polishing. For the larger sample (30×30×2 mm or 9/8× 9/8× 1/16 inch), the four larger openings are left at four corners from the outside, FIGS. 4C, 7B.

X. The cylindrical tool is developed in a few steps almost like trial-and-error method: by adding the possibility of disassembling of cylinders, by reducing the thickness of threads, by enabling the four open corners for the sample corners at the bottom of inner cylinder, by engraving the circular scale at the outer cylinder, notch and the marker at one of the holders ends.

XI. The grinding and polishing procedure is as follows. The tool is assembled such that (one of) inner cylinder is placed in the outer cylinder and fasten with the threaded holder (with a circular plate). In the assembled cylindrical tool, the plate on a holder is first elevated to the same level of the bottom surface of inner and outer cylinder (FIGS. 6B, 7B), with a help of the notch, screwdriver and scale, so that the sample can be placed on its surface. To prevent the sample from falling off the plate, a barely visible layer of a special paste can be applied to the plate surface for a slight sample attachment, if the dry (dry-cured) cement-based sample is tested. If the sample is wet (wet-cured in water), then it is not necessary to use any paste since the thin water layer keeps sample ‘fixed’ to the plate surface.

XII. The plate with a sample is then elevated such that first layer of approximately 0.25 mm ( 1/128 inch), sticks above the bottom of the assembled cylindrical tool surface (thickness controlled via scale and engraved inner notches). The first layer is removed by grinding on the grinding and polishing machine, with two wheels with SiC sandpapers of different granulations. For the initial grinding for the layer removal of 0.25 mm ( 1/128 inch) the SiC paper grit 320 is used. Then the grinding is switched to the SiC paper grit 500. When the grinding is completed and the 1-2 layers of 0.25 mm ( 1/128 inch) are removed, the sample is taken out from the elevated plate for the thickness measurements in a special device with a needle. If the newly measured sample thickness is about 1.5 mm ( 1/16 inch), the sample is returned to the plate and polishing is performed until the sample thickness reaches 1 mm ( 1/32 inch). The polishing is done on SiC paper grit 1200. After polishing of new 1-2 layers, the sample is again taken to the special needle device for the thickness measurements. Grinding and polishing can be done even to the thickness of 0.5 mm ( 1/64 inch) of cement-based sample.

XIII. Grinding and polishing is done by hand, in a few steps, carefully and very precisely holding the cylindrical tool vertically to avoid damaging the sample and to obtain the equally thick sample. The duration of grinding and polishing depends on the sample age, way of curing (wet or dry) and its cement-based composition (concrete/mortar/cement paste). If it is 2-3 days old, the sample can be polished to 1 mm in 10-12 min. If the sample is older (7 days and beyond), it can take up to 20 min.

XIV. Due to the construction of lower part of inner cylinders 8 mm ( 5/16 inch) high, it is possible to place cement-based samples up to 5 mm thickness. The inventor* believes that such stainless steel cylindrical tool could be possibly used for grinding and polishing of samples made of other materials as long as they do not damage the cylindrical tool. *Inventor: MSc. Dragana Janković, Structural Civil Engineer, UCF, FL 

1. Stainless steel cylindrical tool for grinding and polishing thin cement-based samples to 1-mm ( 1/32 inch) thickness and below, further comprising an stainless steel outer cylinder with the engraved rounded scale on its upper side, a threaded vertical opening through the middle of solid part, the circular inner opening of the half-height of outer cylinder at the bottom side that is circularly coated with thin rectangular metal (A1) sheets at a certain distance that are fixed to the interior of outer cylinder in the rounded slots, and ‘ring’-like layer around the lower outer part.
 2. Outer cylinder as in claim 1, further comprising the stainless steel inner cylinder(s) to fit in the outer cylinder in the round opening, one at the time, with vertical threaded opening through the middle of solid part.
 3. Outer and inner cylinder(s) as in claim 2, further comprising a threaded stainless steel holder with the extension in the form of a circular plate at one end, and a notch with a marker at the other end.
 4. Inner cylinder(s) as in claim 2, further comprising the specially shaped squared opening at the bottom, sufficiently deep for fitting in the rounded plate on a holder and sample(s) of two different sizes, one at the time, surrounded by the four inner “walls” with engraved horizontal short marks on all “walls”, with four open rounded corners between four “walls”, for fitting in the four corners of the thin sample(s) that rests on the plate(s), when grinding and polishing is performed. 